Lubrication



- No Drawing.

Application January 221938, 5 SerialNo. 186,299

40mm. te m-m This-invention mates to'lubricants intended forse'rvice in the lubrication or internal combus, tion engines; The invention more particularly.- isconcerned with lubricating or motor oils of 5 mineral hydrocarbon origin which are normally corrosive, toward bearing metal alloys of the, 1 characterjof cadmium-silver, cadmium-nickel, or 1 copper-lead; and has, for an important objective,

the inhibition or prevention-of deterioration 01 tionof the lubricant thereon.

' mi; eonditions of friction and temperature These --'-velopments in internal combustion engines mak-' arings formed of metals or alloys. having great-. r resistance to wear,- and further characterized yhigher'melting'points necessary to prolonged ist ing during operation of the 'engine. Temperatu1resj at the bearing surfaces duringoperation '-,wh.ich Babbitt metal bearings gave satisfactory as es-1e.

I nickel and copp'er 'lead alloys has demonstrated, howeven'that'their utility is greatly impaired by an extremeysusceptibility to rapid deterioration I by thecorrosiv'eaction or efiect of many availabl'e'lubricating oils.- Particularly has this'effect been noted'when the oils are of the charby conventional criteria. Little is known concerning. the nature of. the corrosive action oritscauses; but in generalit has beenob'se'rved that motor oils derived from.

selected crudes predominantly paramnic in ori-. 'gin,,.as well as those oils from these or other :crudesjwhiCh have been improved by treatment "with selective solvents, exhibit a marked tend-' ency' toward corrosion of thebearings in ques- --;t ion, although by other tokens the lubricant is of n50 ---s11perior quality. Oxidation stability, as indi catecl'by sludge or acid formation in conventional tests indicativeiofthe. tendency toward dete- 'rioration of the 011 itself in service, does not ap- .pear to have reliable correlation withthe tendencyof the oil to corrode bearing surfaces. It is possible that the highbearing-surface temperaa T tureslexisting ,under service conditions with the new bearingsmay be a'factor in occasioning the It)v such bearingfmetal in service by the corrosive ac-;

, f Engine bearings comprising or surfaced with 1 -j cadmium silver or like alloys now are frequently employed in lieu of the more usual Babbitt metal bearings; in order tocope with extreme service "conditions are the consequencebf modern de.-"

ng'av'ailable high sustained speeds andrequiring feunderthe extreme thermalconditions ex- C Lmay be and frequently are much higher inthe 1 case-oi engines requiring these} new bearings than I formerlywaskthe circumstance with'engines in v,

-Experience with bearings'ofthe character or type exemplified by cadmium-silver, cadmiumacter generally regarded as superior lubricants invention is particularly concerned, contrasts with problems of lubricant deterioration per so,

since oils'characterized by long life and good or the prevention thereof. as herein proposed According tothe present invention, it has'now been found that the corrosive. effect of lubrieating oils upon bearing surfaces of'the character referred to-above may be avoided in a novel and effective manner by-incorporating with such oils particular compoundshaving a retarding or inhibiting efiect in respect of such corrosion. I More specifically, theinvention arises from the discovery that-'sulfurized organic nitrogen compounds effect a very beneficial retardation of the corrosive action of internal combustion engine nickel, copper-lead andlike bearing metal alloys. It is, therefore, an important object of the 7 present invention to inhibit or retard the corrosive deterioration'of cadmium-silver and like bearing metal alloys in automotive service by providing a lubricant, therefor comprising a refined mineral hydrocarbon oil having incorporated therewith 'a, sulfurized organic. nitrogen compound in small but effective proportions.

Likewise, it is an objector the invention to.

improve, and to prepare improved, motor oils of petroleum origin by incorporating therein a sulfurized organic nitrogen compound in corro- "regarded as encompassing a novel method of lubricating bearing metal surfaces; of the char- .acter of cadmium-silver, cadmiumnickel, copper-lead or like alloys, by applying thereto a film of lubricant comprising mineral hydrocarbon oil having incorporated therewith a small but effec- '0: bearing corrosion, with'which the present according tothe invention, is intend'ed to be reupon. 7

tive proportion'of 'afsulfurize'd organic nitrogen compound. With this method oi'lubrication it has been found thatprolonged life and consequent improved service may be attained the Z use of thesealloys as bearing metals forinternal combustion engines, particularly Whenbperating conditions :such as high sustained speeds-under inVention 'to itS intended service, will be of-a character'generally regarded 35:0! superior grade and refining and one normally corrosive to the aforementioned: type of bearing. Thus, the inregardless of origin.

The sulfurized organic nitrogen compounds useful. in the practice of the present invention comprise, and embrace as a class, reaction products of organic nitrogen compounds, particularly aromatic nitrogen compounds, and elemental sulfur, or compounds containing available reactive sulfur, said products being readily prepared by merely heating together sulfur, or reactive sulfur compounds, and an aromatic nitrogen compound. The expression sulfurized aromatic nitrogen compound as used herein includes, and is intended to include, sulfurized aromatic amines (both mono and.poly aryl derivatives) which, according to accepted nomenclature, are denoted as thio compounds, as well as other sulfur derivatives of aromatic amines which are more properly termed sulfides. The various effective inhibitors which may be selected for use in the practice of the invention are not exact equivalents in that differences in degree of inhibiting effectiveness will be exhibited as between diflerent compounds or groups of compounds falling in the generic class. Oil solubility naturally is of the essence to satisfactory inhibitor action and the invention is to be understood as encompassing within its scope only those members of the broad class which have sufficient solubility in mineral hydrocarbon oil of motor oil character to provide concentrations of inhibitor necessary in each particular instance to supply the retarding or inhibiting action sought.

Illustrative compounds falling within the general class from which inhibitors according to the invention are selected may be mentioned the following:

Thio di-phenylamine Thio di-alpha naphthylamine Thio di-beta-naphthylamine Thio alpha-beta-naphthylami'ne Thio phenyl-alpha-naphthylamine Thio phenyl-beta-naphthylamine Diamino diphenyl mono sulfides (ortho, meta, or

para forms or mixtures thereof) 3,3 diamino dinaphthyl sulfide 4,4 diamino dinaphthyl sulfide Amino phenyl amino naphthyl sulfides Triphenyl amine sulfide Mono-amino diphenyl sulfides Mono-amino dinaphthyl sulfides Diamino diphenyl polysulfldes Efi'ective proportions of inhibitors according to the invention will vary somewhat for different conditions of service and as between different compounds. In the great majority .of cases, however, the necessary quantity of inhibitor added to the motor oil will be very small, ordinarily less than 1% by weight and frequently less than 0.5% by weight; As indicated hereinafter, proportions of the order of 0.2% by weight have proved markedly effective in achieving the objects of the invention. The solubility in mineral hydrocarbon oil of motor 011 character will naturally vary as between the compounds and this will have some bearing upon the proportion of the diflerent members of the class. The stated percentages are not intended in a limitative sense, as obviously the inhibitor may be, and is intended to be, employed in any corrosion inhibiting proportion.

The tendency of motor oils to corrode bearings of the character in question may be determined by a convenient test which affords a ready method of obtaining a comparative evaluation of motor oils in the laboratory. In this test method a group of bearings, ordinarily including at least one each of several of the newer bearing metal alloys (viz: cadmium-silver, cadmium-nickel and copper-lead) is supported in a chamber in which air may circulate and the bearing surfaces are exposed for a' period of 22 hours to a stream of oil sprayed under pressure continuously upon the corrodible area. The oil is maintained at a temperature of approximately 335 F. and the spray is so directed as to disperse oil over the surfaces of the bearings. Means are provided for recirculating the sprayed oil so that a given quantity is used for a given test, thus simulating service conditions in an engine. The measure of corrosion is taken as the loss in weight of the bearings per unit of exposed corrodible surface.

The test method described above is carried out in the familiar Underwood corrosion apparatus supplied by the Scientific Instrument Company of Detroit, Michigan, in accordance with General Motors specifications.

Results secured utilizing the foregoing test for comparative evaluation of motor oils with and without an inhibitor according to the invention provide specific illustration of the value and inhibiting effectiveness of compounds as herein disclosed. The oil used for the tests was an S. A. E. motor oil comprising a blend of wellrefined parailinic base stocks and having an A. P. I. gravity of 30.1, Sayboltviscosity at 100 F. of about 300 seconds, Saybolt viscosity at2l0 F. of about 54 seconds and flash point of 425 F. To portions of such an oil were added 0.2% by weight of inhibitors according to the invention. During each run cadmium-silver, cadmiumnickel and copper-lead bearings all were present; and comparative losses in weight per square decimeter due to corrosion were determined for the respective bearings.

The results obtained in five illustrative tests will suffice to demonstrate the inhibiting effectiveness of the class of compounds herein disclosed.

Test I .Thio di-phmylamine Test II.-Thio di-beta-naphthylamine Oil plus Bearing inh bitor Grams Cadmium-silver: Cadmium-nickel Copper-lead Test 111.4% dt-alpha-naphthylamin'e lus ' on on Ewing blank mm ltor Cadmium-silver Cadmium-nickel Copper-lead Test IV.Thio phenyZ-alpha-naphthylamine on ins Bearing blank inhi i tor Grams Gram Cadmium-silver Cadmium-nickel 6. Copper-l 0.

Test V.Diamino diphenyl mono sulfide (mixture of ortho and para forms) Oil blank Oil lus Bem'ng mm m Grams N 0 loss Do. Do.

Grams Cadmium-silver 6. 5 Cadmium-nickel 7. 5 Copper-lead 0. 9

1 above; and operated under carefully controlled conditions duplicated in successive runs with and without inhibitor present in the lubricating oil. New bearings carefullyweighed were used for each run, and each set comprised alternate cadmium-silver and copper-lead bearings respectively. Operating conditions included an engine speed of 2850 R. P. M. under a load of brake horsepower and a running period of 15 hours, this being the equivalent of 768 miles travel at a speed of 51.2 miles per hour. Crankcase oil temperature was maintained at 300 F. and water temperature at 200 F. The oil consequently was subjected to lubricating service far more severe than that normally to be encountered in ordinary automotive use. At the end of each run the bearings were removed and again weighed, the loss in weight giving a measure of corrosion caused by the lubricant.

' Tested in an engine under the foregoing conditions an S. A. E. 20 motor oil, of the character and specifications used in the laboratory evaluations hereinbefore reported, gave the following results:

Milllilgtramstiosshiln weig per ear g Inhibitor.

None 0.1% thio dl-phenylamine.

one 0.2% thio phenyl-alpha-naphthylamine....

The foregoing results obtained in exploratory practice of the invention under test and service conditions of accentuated severity clearly evidence the operative significance of the disclosed class of compounds as. valuable additions to motor oils intended for service in the lubrication of engines equipped with cadmium-silver and like alloy bearings. Inspection of the comparative data presented in the several foregoing tables shows a substantially complete suppression of corrosion when the inhibitor is used in pro-' When, as in the second engine I portions of 0.2%. run above using thio di-phenylamine as a bearing corrosion inhibitor, the proportion of in hibitor is reduced from 0.2% to 0.1%, a marked suppression of bearing corrosion still ensues, the loss in weight per bearing due to corrosion being but one-third of the loss encountered when no inhibitor is used. For many circumstances of normal automotive use it is likely that rather small percentages of inhibitor will 'sufflce for complete protection since operating conditions ordinarily encountered are not as stringent as those of the testruns herein. I

While the utility of the invention has been illustrated specifically with reference to aparticular motor oil, no limitation is to be inferred therefrom, and other oils, whether or not comparable in specification or origin, may be used in the lubrication of bearings of the type described in accordance with the invention.

This application includes the disclosure, and may be regarded as in part a continuation, of my co-pending applications, Serial No. 114,117- filed December 4, 1936, and Serial No. 131,787- filed March 19, 1937, in which applications inhibitors comprising the compounds thio diphenylamlne and thio di-beta-naphthylamine are claimed specifically.

I claim:

1. The method of lubricating bearing surfaces, at least one of which is formed of an alloy having substantially the corrosion susceptibility characterizing to the bearingsurfaces lubricant comprising a mineral hydrocarbon oil normally tending to corrode such alloys and having incorporated therein corrosion inhibiting proportions of a compound selected from the group consisting of: thio dialpha-naphthylamine; thio di-beta-naphthylamine; thiov alpha-beta-naphthylamine; thio phenyl-alpha-naphthylamine; thio phenyl-betanaphthylamine; diamino diphenyl mono sulfides; 3, 3' diamino dinaphthyl sulfide; 4,.4' diamino dinaphthyl sulfide; amino phenyl amino naphthyl sulfides; triphenyl amine sulfide; monoamino diphenyl sulfides; mono-amino dinaphthyl sulfides; diamino' diphenyl polysulfides.

2. The method of lubricating bearing surfaces, at least one of which is formed of an alloy having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel and copper-lead alloys, which comprises applying to the bearing surface lubricant comprising a mineral hydrocarbon oil normally tending to corrode such alloys and having incorporated therein corrosion inhibiting proportions of thio di-alpha-naphthylamine.

3. The method of lubricating bearing surfaces, at least'one of which is formed of an alloy having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel and copper-lead alloys, which comprises applying to the bearing surfaces lubricant comprising a mineral hydrocarbon oil normally tending to corrode such alloys and having incorporated cadium-silver, cadmium-nickel; and copper-lead alloys, which comprises applying 4- genomes therein corrosion inhibiting proportions of thio the bearing surfaces lubricant comprising a.

phenyl-alpha-naphthylamine. mineral hydrocarbon oil normally tending to cor- 4. The method of lubricating bearing surfaces, rode such alloys and having incorporated therein at least one of which is formed of an alloy having corrosion inhibiting proportions of diamino substantially the corrosion susceptibility chardiphenyl sulfide.

acterizing cadmium-silver, cadmium-nickel and copper-lead alloys, which comprises applying to ARTHUR WALTHER LEWIS. 

